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ANATOMY   OF   THE   CRESTED   RAT                  CHAP.
Sub-Fam. 6. Dendromyinae.—The genus Deomys is an Afri-
can form, consisting of only one species from the Congo region.
D. ferrugineus has a reddish colour as its name implies; the soles
are quite naked and the tail is long and slender. It is con-
siderably longer than the body, measuring (minus a fragment of
the tip) 172 mm., while the body is 125 mm. long. The
characters of the molar teeth, which are three, are intermediate
in their form between those of the true Rats and those of the
Dendromys is also Ethiopian in range. There are several
species. D. mesomelas is a smallish creature, 60 mm. long, with
a tail of 90 mm.
Steatomys is another African genus, allied to the last. Its
tail, however, is only half the length of the body. The two
remaining genera are Mcdacothrix and Limacomys. Their range is
Sub-Fans.. 7. Lophiomyinae.—Allied to the Hamsters is the
singular East African, genus Lophiotnys, with only one species,
L. imhausi, of Milne-Edwards.1 The size is between that of a
Rabbit and of a Guinea-pig. The stomach is curved and somewhat
Intestiniform. It has been termed the Crested Rat on account of
the " prominent crest of stiff hair running down the back." The
fingers and toes are five, and the very long tail is clad with hair
longer than that upon the body generally. The pollex is rudi-
mentary, and the hallux is opposable.
The most remarkable structural feature in this genus con-
cerns the skull, and on account of this it has been regarded as
the type of a separate family. The temporal fossa behind the
eye is covered over by a complete bony plate, formed by a down-
growth of the parietal, meeting an upgrowth from the malar;
this singular arrangement of the bones recalls the conditions
which obtain in turtles. The whole skull, moreover, is covered
with symmetrically disposed granulations, such as are found in
no other mammal; it suggests rather the skull of certain fish.
It is believed that the bony plate already referred to is not really
a portion of the bones of which it appears to be a prolongation,
but merely an ossification of fasciae in this region. The atlas
is granulated like the skull; there are sixteen pairs of ribs and
a feeble clavicle. The molars are three, and of a peculiar form*
1 Nvwo. Arcfc. Mns. iil. 1867, p. 81.